Conventionally, in an electrophotographic image-forming apparatus such as a copying machine, a printer, and a facsimile, an image is formed on a sheet, in accordance with image data supplied from a peripheral device.
In such image-forming apparatus, a positional error (mispositioning, shifting) of a image-forming position of an image with respect to the sheet is attributed to a misalignment between (a) a position (feeding position) to which the sheet is fed from a feeding means that is for feeding the sheet; and (b) a position of the image formed on an image-holding body (photosensitive drum) in accordance with the image data. This mispositioning is corrected by adjusting the feeding position of the sheet to its predetermined position, and adjusting the image-forming position to its predetermined position. The mispositioning is also corrected by adjusting one of (a) the position of the image formed on the image-holding body and (b) the feeding position of the sheet being fed, so as to match with each other. In addition to the positional error of the image-forming position, a copy-scale error sometimes takes place in forming the image.
In any of countermeasures described above, however, an amount and a status of the positional error on the sheet is first checked by visual check or by using an image-reading apparatus, in order to correctly evaluate the positional error that is taking place. The image-forming apparatus is then adjusted according to the evaluation result. This adjustment is carried out (a) when the image-forming apparatus is manufactured, (b) when the image-forming apparatus is installed by a service person, or (c) by the service person or a person in charge of assembling and adjusting, when exchanging a part or a unit relevant to the image forming.
Japanese Unexamined Patent Application, publication No. 125314/1995 (Tokukaihei 7-125314; published on May 16, 1995), discloses an arrangement in which an image-forming position on the sheet is adjusted by (a) outputting reference image data, which is preliminarily recorded in an image-forming apparatus, and (b) reading, by using an image-reading apparatus, the image thus outputted.
Further, Japanese Unexamined Patent Application, publication No. 186994/1998 (Tokukaihei 10-186994; published on Jul. 14, 1998) discloses an arrangement in which adjustment of an image-forming position on the sheet is carried out by (i) forming an unadjusted image, and then (ii) reading an unadjusted image by using an image reading means.
Further, Japanese Unexamined Patent Application, publication No. 271275/1988 (Tokukaisho 63-271275; published on Nov. 9, 1988) discloses a method of detecting a pattern formed on a feeding belt.
However, in the conventional arrangement described above, the adjustment requires a correctly-preadjusted reading apparatus, which has no positional error of reading position as a result of the correct preadjustment.
Namely, as disclosed in Tokukaihei 7-125314 and Tokukaihei 10-186994, reading of a chart of the image (to be used as a reference) by using an image-reading apparatus, which is a peripheral device, requires the correctly-preadjusted reading apparatus which has no positional error of reading position. Further the correctly-preadjusted image-reading apparatus which has no positional error of reading position is also necessary, when using the reading apparatus to read an image formed by outputting the reference image data, which is preliminarily recorded in the image-forming apparatus.